You are Here: Home >< Maths

# Calculus - rates of change watch

1. Hi,

I was just wondering if the way I worked out this question is correct.

Basically I subbed in 4 into the dT/dt equation and then the answer I got from that I added it to -7. Is this correct ?

Thanks
Attached Images

2. (Original post by Olive123)
Hi,

I was just wondering if the way I worked out this question is correct.

Basically I subbed in 4 into the dT/dt equation and then the answer I got from that I added it to -7. Is this correct ?

Thanks
They are asking for the temperature at the end of 4 hours. Subbing 4 into will give you the rate at which the temperature is increasing with time.

To get back to an equation involving the temperature, what would you do to the equation? A hint is in the spoiler.
Spoiler:
Show
Hint: Try integrating the differential equation to form a linear equation involving T and t.
3. (Original post by Dapperblook22)
They are asking for the temperature at the end of 4 hours. Subbing 4 into will give you the rate at which the temperature is increasing with time.

To get back to an equation involving the temperature, what would you do to the equation? A hint is in the spoiler.
Spoiler:
Show
Hint: Try integrating the differential equation to form a linear equation involving T and t.

So after integrating should I sub in T=-7degrees to get the constant?

Should I then use the temp equation I got from integrating and sub in t=4 to find the temp at the end of 4 hours ?
4. (Original post by Olive123)
So after integrating should I sub in T=-7degrees to get the constant?

Should I then use the temp equation I got from integrating and sub in t=4 to find the temp at the end of 4 hours ?
Yes, you would sub in T = -7 and t = 0 (as the temperature is initally -7 degrees), and then use the equation you got from integrating.
5. (Original post by Dapperblook22)
Yes, you would sub in T = -7 and t = 0 (as the temperature is initally -7 degrees), and then use the equation you got from integrating.
Thanks a bunch
6. Forget the question! Look at the hyperbolas the pixels on your screen are making
7. (Original post by Sinfire)
Forget the question! Look at the hyperbolas the pixels on your screen are making
Nice observation ha
8. Yes as long as your units of time are correct. As T(t) is the form of the equation f(x) I.e. The function of x will produce a temperature which is proportional to e to the power of the time taken including any coefficients.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: August 11, 2016
Today on TSR

### Three reasons you may feel demotivated right now

...and how to stay positive

### Can I get A*s if I start revising now?

Discussions on TSR

• Latest
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE